The present invention relates to drive circuits for infrared remote control transmitters.
Infrared remote control systems for television receivers and the like are known. The chief advantage of infrared remote control systems in comparison to ultrasonic remote control systems is that they are less susceptible to erroneously-generated interference signals. Unfortunately, the human eye may be harmed under conditions of prolonged, continuous and direct exposure to infrared radiation.
In order to reduce the possibility of harm to the eyes of users, infrared remote control systems utilize special pulse codes which minimize the duration of infrared radiation during the transmission of remote controlled messages. However, since in conventional drive circuits for infrared remote control transmitters the infrared light source, e.g., a light-emitting diode or diodes, is typically included in a direct current path from a supply voltage, infrared radiation may be continuously emitted should there be a component failure in the remote control transmitter. Therefore, there is a requirement for drive circuits for use in infrared remote control transmitters in which component failures do not result in the continuous emission of infrared radiation. The present invention concerns such a "fail-safe" drive circuit.